参考所有分组，完成尽量多的内容。禁止顺手扩功能 smoke：锁定OPFS参数保存顺序

结论：按 LinuxCNC rs274ngc_pre.cc save_parameters() 的 .new、.bak、unlink/link/rename 顺序补强 OPFS/app/browser smoke 守卫，并验证临时参数文件不会残留在 OPFS。

web/test-browser-wasm-smoke-app-sections.js

@@ -39,6 +39,13 @@ export async function runBrowserAppOpfsSections(context) {
       const updatedParameterFile = new TextDecoder().decode(await appSimulator.fs.opfs.readFile("parameters/rs274ngc.var"));
       expectIncludes(updatedParameterFile, "5161\t2.000000",
         "app frame did not replace LinuxCNC parameter state after second parse");
+      // LinuxCNC source basis: rs274ngc_pre.cc save_parameters()
+      // renames filename + ".new" over filename after a successful save.
+      await context.expectOpfsMissing(
+        appSimulator,
+        "parameters/rs274ngc.var.new",
+        "app frame did not clean up LinuxCNC temporary parameter file in OPFS",
+      );
       const savedParameterBackup = new TextDecoder().decode(await appSimulator.fs.opfs.readFile("parameters/rs274ngc.var.bak"));
       expectIncludes(savedParameterBackup, "5161\t1.000000",
         "app frame did not persist LinuxCNC parameter backup into OPFS");